The studies involved in this program project will focus on several specific nutrients -- beta-carotene, vitamin A, and vitamin E. Because of the interactions of other dietary factors with these nutrients, it is important to assess overall dietary quality and to monitor for confounding and interacting nutrients. The objective of the Dietary Core is to consolidate resources and provide support needed for adequate dietary assessment in the associated projects, and to conduct research required for continuing refinement of the dietary methodology appropriate to cancer control projects. Specific aims include 1) supervision of the design and collection of all dietary data; 2) maintenance and ongoing development of appropriate food composition data bases; 3) reduction of dietary data (coding and conversion to nutrients or compounds of interest); 4) provision of reduced data to project investigators, working in close collaboration with the Biometry and Information Processing Core; 5) consultation with the project investigators regarding interpretation of dietary results; 6) maintenance of quality control procedures for dietary assessment data collection, coding, and analysis; and 7) methodologic investigation in support of the projects.